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Description: Ginning industries, spinning mills and other composite textiles industries produce a lot of cotton waste annually. This waste is rich in cellulose and solid contents with sufficient carbon to nitro...

Ginning industries, spinning mills and other composite textiles industries produce a lot of cotton waste annually. This waste is rich in cellulose and solid contents with sufficient carbon to nitrogen ratios. However a lot of chemicals are already present in cotton waste at the end of various processes like dyeing, finishing, washing, etc. This reduces the fuel value of cotton by lowering down its calorific value. The calorific value (or energy value or heating value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. Improving the calorific value of cotton by anaerobic digestion is an environment friendly approach of converting waste to energy.

Abstract--Ginning industries, spinning mills and other
composite textiles industries produce a lot of cotton waste
annually. This waste is rich in cellulose and solid contents
with sufficient carbon to nitrogen ratios. However a lot of
chemicals are already present in cotton waste at the end of
various processes like dyeing, finishing, washing, etc. This
reduces the fuel value of cotton by lowering down its
calorific value. The calorific value (or energy value or
heating value) of a substance, usually a fuel or food (see
food energy), is the amount of heat released during the
combustion of a specified amount of it. Improving the
calorific value of cotton by anaerobic digestion is an
environment friendly approach of converting waste to
energy.
I. INTRODUCTION
The textile production and its application have been
increasing drastically worldwide in the past few years. The
total fibre production in the year 2011 was more than 51
million metric tons of man-made fibres and nearly 30
million metric tons of natural fibres. The record-high total of
81 million metric tons represents a 1-percent increase over
2010 fibre usage, and per-capita consumption of nearly 12
kilograms [1]. All these used textiles end up as waste sooner
or later in a waste collection station, and these wastes are
generally incinerated or land filled. In many countries
including European nations, land filling of organic waste is
forbidden (The council of European nations). Textiles
wastes are usually converted to fuel by pyrolysis technique,
this however generates huge amount of fumes and smoke
[3]. This waste is rich in cellulose and other solid nutrients
and can effectively generate biogas, which can act as a fuel
for lighting, cooking, running diesel engines and the
remnant slurry acts as a manure for agricultural purposes.
The basic gas producing reaction in these digesters is
2C+2H
2
O=CH
4
+CO
2
[2]. Biogas from cotton waste is a
simple, economic and environment friendly method to
overcome the problem of cotton waste which is increasing
day by day. Cotton waste is converted to biogas by the
Anaerobic Digestion. Bacterial digestion decomposes the
cellulose present in the cotton waste to methane (CH
4
).
Also, it is about 20% lighter than atmospheric air and has an
ignition temperature in the range of 650°C to 750°C. It is an
odourless and colourless gas that burns with clear blue flame
similar to that of Liquefied Petroleum Gas and burns with
60% efficiency in a conventional biogas stove [4]. Biogas
technology involves four main processes hydrolysis,
acidogenesis, acetogenesis, and methanogenesis. Hydrolysis
is the primary step in the formation of biogas, in which
complex organic (long chain) materials such as
carbohydrates, proteins and lipids are broken down to
simplest (small chain) compounds like sugars, amino acids
and fatty acids using hydrolytic bacteria. Acidogenesis is the
second phase in the biogas formation process. In this phase,
all the monomers are converted into VFA’s (volatile fatty
acids). Mainly acidogenic bacteria are responsible for
producing VFA’s such as Valeric acid, Butyric acid,
Propionic acid, Caprionic acid, Isovaleric acid etc. Many
groups of bacteria are responsible for the hydrolysis and
acidogenesis process which mainly belong to the family
Streptococcaceae and Enterobacteriaceae and genera of
Bacteroides, Clostridium, Butyrivibrio, Eubacterium,
Bifidobacterium, and Lactobacillus. In the acetogenesis
process, all the VFA’s compound, ethanol and aromatic
compounds like benzoate are converted into the acetic acid,
hydrogen and carbon dioxide using acetogenic bacteria. In
the methanogenesis process, methanogenic bacteria use
acetate, hydrogen and carbon dioxide as a substrate for the
production of the methane [5]. After the biogas is generated
the residual slurry should be tested for its constituents.
Mainly the calorific value to give an improved fuel value,
low ash percentage, BOD, COD and other such tests.
Calorific Value A.
The calorific value (or energy value or heating value) of a
substance, usually a fuel or food (see food energy), is the
amount of heat released during the combustion of a
specified amount of it. The energy value is a characteristic
for each substance. It is measured in units of energy per unit
of the substance, usually mass, such as: kJ/kg, kJ/mol,
kcal/kg, Btu/lb. Heating value is commonly determined by
use of a Bomb Calorimeter. [6]
The calorific values of some known non-renewable and
renewable fuels are mentioned in Table. 1:
Fuel
Approx heating value
(Kcal/Kg)
Natural
State
Dry
state
BIOMASS

860
Bio gas(Kcal/cu mtr) (12 kg of
dung produces 1 cu. Mtr gas)
4700-6000
Table. 1: Calorific Value of Fuels [7]
Ash Content (%) B.
In analytical chemistry, ashing is the process of
mineralization for pre-concentration of trace substances
prior to chemical analysis. Ash is the name given to all non-
aqueous residue that remains after a sample is burned, which
consists mostly of metal oxides. Ash is the waste product of
fire. Ash is one of the components in the proximate analysis
of biological materials, consisting mainly of salty, inorganic
constituents. It includes metal salts which are important for
processes requiring ions such as Na+ (Sodium), K+
(Potassium), and Ca
2
+ (Calcium). It also includes trace
minerals which are required for unique molecules, such as
chlorophyll and haemoglobin. [8]
II. EXPERIMENTAL SETUP
Raw Material A.
Textile Waste was collected from Arvind Limited, Naroda,
Ahmedabad, which is a composite denim manufacturing
industry. Wastes samples were collected from different
departments. Material to water ratio must be maintained to
1:2 for higher gas generation. Waste samples included
cotton waste like fibre waste from spinning department, yarn
wastes from winding, sizing and dyeing department, fabric
wastes from weaving department. In addition to this Fluff
which is the deposition of fibres in warping, sizing, dyeing
and weaving departments, was collected. It needs to be
scrapped off from the surfaces it clings to, as it forms a thick
condensed layer on the walls and machinery of the
departments. Sludge cakes were also collected which is the
end product of the effluent treatment plant and is a
condensed fibre cake. This is sent to the landfills after
compression and cannot be utilized further.
The details of the acquired sludge cakes are
mentioned below in Table. 2.
Parameter Values
pH 7.2
COD gm/kg 850
BOD gm/kg 270
Table. 2: Sludge Cake Details
Pre-treatment Methods B.
The cotton waste from different departments was collected
and mixed for uniformity among all samples. It was
weighed and placed in the air-tight container. Pre-treatment
of cotton was classified in two major categories as below,
mainly to break the crystalline region of cotton and achieve
better hydrolysis, which in turn reduces the number of days
required for anaerobic digestion.
(i) Acid Hydrolysis
5% Acid of the total raw material in the air-tight plastic
container (H
2
SO
4
and HCl) was selected.
(ii) Alkali Hydrolysis
20% Alkali of the total raw material in the air-tight plastic
container (NaOH and NH
3
) was selected. Raw material was
pre-treated for 5 days to break down the crystalline region of
the cotton. The pH of all the samples after 5 days was
measured and neutralised.
Seeding Material C.
After neutralising the pH, seeding material was added to the
pre-treated raw material containers to initiate bacterial
activity. Seeding materials used were cow dung and
cellulase enzymes.

Fig. 1: Lab Scale Trial
Gas generation was measured till the digestion process was
over by the 47
th
day. The generated gas was collected in gas
bags and tested on the gas chromatograph (GC) for the
percentage of gases present in it.
III. TESTS
Calorific Value A.
Heating value is commonly determined by use of a Bomb
Calorimeter. [6]
Ash Content (%) B.
Ash was calculated after calorific value was tested. Both
calorific value and % ash content were tested by the below
listed method.
IS 1350 (Part 1): 1984 Methods of test for coal and 1)
coke: Part 1 Proximate analysis (second revision)
(Amendment 1).
IS 1350 (Part 2): 1970 Methods of test for coal and 2)
coke: Part 2 Determination of calorific value (first revision)
To Improve the Calorific Value of Cotton Waste by Anaerobic Digestion
(IJSRD/Vol. 1/Issue 3/2013/0065)

All rights reserved by www.ijsrd.com
658
(Amendment 1) method were adopted to estimate the
percentage ash content and the calorific value of the residue.
IV. RESULTS
Calorific Value A.
The calorific value of all the samples was tested on the
Bomb Calorimeter. The calorific value of pure cotton is
tested to be 3845.8 cal/gm. The results are shown in Table.
4.
Sample Calorific Value (cal/gm)
A 4037
B 4026
C 4019
D 4310
E 4151
F 2435
Table. 4: Calorific Value Results
Calorific value of all samples with cow dung as the seeding
material improved. Sample F was seeded with enzyme and
shows poor performance. The same results are expressed in
Graph 1 below:

Graph. 2: Ash Content (%).
V. CONCLUSIONS
The biogas setup was simple and helped to generate gas
efficiently at our university lab. Careful measurements must
be taken to avoid gas leakage from the lab-scale model
during the digestion phase. After this the residual slurry was
tested for its calorific value and ash content (%) to derive its
fuel value.
Pre-treatment can be adopted as a solution for
cotton wastes with chemicals present in it. It was an attempt
to estimate the calorific value potential of cotton wastes
after anaerobic digestion.
Trials with different chemicals for pre-treatment
proved advantageous to break down the crystalline region of
cellulose present in cotton. This ceased the activity within
45-50 days.
7.5% of cow dung with cotton waste by weight was
added to the cotton waste to improve its digestion rate and
calorific value. Cow dung initiates the bacterial activity in
the digestion process effectively.
Ash content (%) was closer to the standards.
Using enzymes in place of cow dung as a seeding
material did not serve any purpose for sludge cakes.
ACKNOWLEDGEMENT
I sincerely thank Prof. A.I. Thakkar, Head Textile
Technology Department, LD College of Engineering and
Prof. N.S. Varandani, Head Environment Engineering
Department, LD College of Engineering for their patient
guidance, enthusiastic encouragement and useful critiques of
this research work and to the technicians of the laboratories
I contacted for the measurements of some parameters and
their rightful data analysis.
REFERENCES
[1] The Fibre Year 2012 Textiles/Nonwovens Survey –
Textile World.
[2] V. Balasubramanian, K. Sridhara, and V. Ganesan,
“Performance evaluation of small agriculture engine
operating on dual fuel (Diesel + Natural gas) system”
SAE international, 951777, September 1995.
[3] Master Thesis: “High rate biogas production from
waste textiles” by Karthik Rajendran & Gopinath
Balasubramanian University of Boras (Year 2011).
[4] Bio Gas from Textile Cotton Waste - An Alternate
Fuel for Diesel Engines by C. Sundar Raj, S. Arul, S.
Sendilvelan and C.G. Saravanan.
[5] Master Thesis: “High rate biogas production from
waste textiles” by Karthik Rajendran & Gopinath
Balasubramanian University of Boras (Year 2011).
[6] http://en.wiktionary.org/wiki/calorific_value
[7] http://www.indiasolar.com/cal-value.htm
[8] http://en.wikipedia.org/wiki/Ash_(analytical_chemistr
y)

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